Sun. Eve.: A Quiet Week for the Most Part

Synopsis

A weak cold front and upper-level trough will slide through on Monday, bringing a few rain or snow showers to the Commonwealth during the day. Our friendly northwest-to-southeast flow will bring low-level clouds and an occasional breeze during the first half of the week. Then, high pressure moves in on Thursday, which should keep us dry for the weekend despite a low pressure system sliding out to sea Friday night. Temperatures should warm up starting on Tuesday, ramping-up after the clouds clear.

Models Used: 18z GFS, 00z & 18z NAM & Hi-Res NAM, 12z ECMWF; Diagnosis: Models are reliable with good agreement between them.

Short-Term

Cloudy skies and a passing shower will keep the temperatures down to start the week. Most of the precipitation will be pre-frontal with snow, rain and graupel possible given the freezing level is around 925 mb. A lake-effect snow shower is possible across northwestern PA during the early part of the work week. Accumulations will be light in most cases, even with the lake-effect precip. Winds will be a factor during the afternoon and early evening hours on Monday, Tuesday and Wednesday.

Long-Range

Most models are taking the upper-level trough currently over California pretty much from west to east. The track of this system on Friday and Saturday takes this out to sea, with a rain or snow shower possible near Philadelphia according to both the Euro and GFS. It bears watching, but right now, high pressure looks to be in control for the end of the work week into the weekend. Above average temperatures are likely to accompany the new airmass.

-Jaron Breen

Thursday Morning Forecast

Synopsis:  Temperatures will finally begin to moderate a bit as we head into Easter Weekend. We can expect temperatures in the upper 40s to around 50 as we head into Friday and Saturday. Today it will remain cloudy with a slight chance of a rain/snow shower. Our next storm system will them approach from the southwest on Sunday. Unfortunately, it appears that we will have some nasty weather on Easter. That storm system will then move out on Monday with just a chance of lingering rain and/or snow showers. Thereafter it looks like we will remain storm free for a while with temperatures climbing into the lower 50s.

Short Term:  It looks like this will be the last day we have to deal with the persistent NW flow we've experienced for the past few days from a stubborn low up to our northeast. Before our next big system moves through, a weak ridge looks to build over the region, providing a decent amount of sunshine and seasonable temps.

Long Term:  Our next system will be associated with a cutoff 500 mb disturbance swinging down through the Great Lakes. According to recent GFS, it's associated surface low isn't forecast to make it's way into the US, but instead swing down toward the Great Lakes and then back north into Canada. But, we will see the effects of its frontal systems, though. Once the cold front passes through the region, providing us with mixed rain and snow showers, the 500 mb disturbance becomes more amplified, inducing the birth of a secondary low in the cold front of the original system. Models are not quiet sure how to handle this secondary disturbance, which is currently forecast to develop over the Carolina's and ride the coast up into the Canadian Maritimes. Should models tend towards strengthening of this system, areas on the East Coast (including eastern PA) should remain alert for additional snowfall (yes, snow) and mixed precipitaton.

Thursday M

Wed Night

Synopsis: Gloomy conditions and below average temperatures will last through the end of the week with a slight warm up to normal by the weekend. Another shot of cold air is expected early next week, prolonging winter into the foreseeable future.

Short Term: Snow and rain showers will slowly wind down overnight as stability increases. Temps will fall into the 20s, statewide, which is much below normal for this time of year. Scattered rain/show showers will persist through tomorrow as northwest flow blows across the lakes.

Long Term: NW flow around a relentless upper level low to our north will keep conditions dreary and cold until late week. A weak high pressure will move into the area for the start of the weekend, bringing a slight warm-up and the most sun we have seen in a while. However, another storm system will move to our north and drop a cold front through by the start of next week. This will allow a deep upper level low to move in and keep wintry conditions around for the foreseeable future! Some model guidance is suggesting another winter storm late next week, however, there is much uncertainty in this solution.

Monday Night Technical Discussion

Synopsis

 

As the snow showers dissipate tonight across the state, a northwesterly flow will set up for the rest of the week and provide a chance for scattered snow showers for central and western Pennsylvania. High pressure will make its presence Saturday and for the first half of Sunday as clouds finally clear for the majority of the state. This will bring a return southwesterly flow and finally allow temperatures to rise near normal, which at the moment is in the upper 40's to lower 50's statewide. However, clouds will make their way back into the area Sunday afternoon as a system passes to our north, which could bring some mixed precipitation across the state.

 

Short Term (Monday night thru Tuesday)

 

Snow showers will begin to dissipate overnight as both the 18Z NAM and GFS agree with precipitation ending around 06Z Tuesday. As the low pressure continues to move off the east coast a northwesterly flow will set up and provide western PA with scattered lake effect snow showers for the rest of the week. Portions of central Pennsylvania could see these showers mix with rain at times this week as temperatures should rise close to 40 degrees under partly sunny skies.

 

Long Term (Wednesday into the ­weekend)

 

As the northwesterly flow persists and scattered lake effect snow and rain showers continue to affect central and western portions of the state, eastern PA will likely see partly cloudy and windy conditions Wednesday. The flow should weaken later this week as high pressure starts pushing east into the region. As it does so, scattered lake effect snow showers will dissipate Friday morning and clouds will clear across the state. Saturday and Sunday morning look rather calm as high pressure moves in and high temperatures will reach the 50's for much of the state. We will need to keep an eye out for Sunday afternoon, as the 18Z GFS is showing a low pressure system moving just north of the state and bringing a chance for mixed precipitation for extreme northern portions of the state and rain showers for the rest of PA.

~A.J. Herbert

Sun. Eve: More Snow

Synopsis:

Two low pressure systems will bring snow to most of the Commonwealth between now and Tuesday morning. One of the lows is off the east coast of North Carolina, which will wasn't much of a factor. The other is over eastern Kentucky, which, as of 03z, was bringing snow to southwestern PA. Once this clears out, northwest flow will dominate the forecast for much of the work week, meaning lake-enhanced, back-end snows and lake-effect precipitation at least through Thursday. High pressure will slowly move overhead, arriving on-time for the weekend.

Models Used: 12z ECMWF, 15z SREF, 18z GFS, 18z & 00z NAM & Hi-Res NAM; Preference: General Model Consensus

Short-term:

Precipitation should start to fall across the remainder of the state from southwest to northeast by 09z or 12z (daybreak) and taper after nightfall Monday. When all is said and done, about 3-7 inches should fall in southwest PA, 2-4 inches in northwest and central PA, 1-3 inches in northeast PA, and 3-5 inches in southeast PA. Then, the northwest flow sets-up, bringing more dreary weather for Tuesday & Wednesday with accumulating snows for western PA likely.

Long-Range:

Not much to discuss in the long range outlook as a large ridge of high pressure gradually moves into the state over the course of the week.

-Jaron Breen

Thursday Afternoon Discussion

Synopsis: Cold air will continue to filter in from the north over the next few days as a disturbance to the northeast slowly begins to move out of the region.  Drier air moves in for the weekend with another disturbance brushing by to our south early next week.

Short Term:  A northwesterly flow has dominated the area today allowing for lake enhanced clouds to filter in.  Also surface heating in the morning and cold air aloft allowed for clouds to develop across inland portions of the state.  With an unfrozen lake Erie and 850-1000mb temperatures below -13°C, lake effect snow showers are expected in the northwestern portion of the state as the flow over the lake dominates through Friday.  For the rest of the state, snow showers will not likely make it past the ridge line in the center of the state allowing for dry and partly sunny skies to hold into Saturday.  Temperatures will remain below average.

Long Term:  Saturday will be mostly sunny across the state as our lingering disturbance in the northeast finally moves out.  Dry air will filter in allowing for clouds to dissipate.  Temperatures will still remain below average as no significant warm air advection is expected.  Clouds increase for Sunday as our next disturbance begins to take shape and move into the region.  Sunday night is when precipitation is likely to start as the disturbance brushes by to our south.  Light snow showers are expected for much of the state but some rain may mix in down by the PA/MD border.  Below average temperatures are expected through all of next week.

Thursday Morning Discussion

Thursday Morning Discussion

Synopsis:  Today will feature chilly, breezy conditions with a chance of snow showers throughout the day.  As we look ahead we can continue to expect below normal temperatures throughout the forecast period.  Along with the unseasonable cold temperatures, we will have storm chances every few days.  The next major storm system appears as if it will affect the region as we move into early next week, although it may totally miss considering that it is almost 5 days out.

Short Term:  Expect very cold temperatures today.  The high may not even make it above the freezing mark, which is very rare for this late in the year.  Along with the very cold temperatures, expect a threat for scattered. lake enhanced snow showers as the cold, dry wind crosses over the relatively warm Great Lakes.  The threat for snow showers will diminish as  we move into tomorrow.

Long Term:  It looks very stormy and cold in the long run.  On both the ECMWF and the GFS the 540 line does't come north of State College for the entire next week!  With this very cold air overhead it won't take much to create some instability, so expect cloudy conditions for the majority of the time.  Our next big storm systems enters the region on Monday.  Both the ECMWF and the GFS have us getting several inches of snow, so this storm system bears watching.

Tuesday Evening

Synopsis: The low pressure system that brought us a few inches of snow and mixed precipitation will continue to bring snow showers and unsettled weather to the commonwealth for the next few days. A persistent northwesterly flow will continue. As the closed off upper level low scoots to the northeast, another low pressure will move in from the south, leaving little down time in between. 

Short Term: Snow showers continue to move across the state overnight. Generally snow showers are not making it past the middle of the state. Otherwise, the northwest flow will bring cloudy, breezy, and cooler weather. Lake effect snows will continue in the northwestern parts of the state through the end of the week.

Long Term: Our next systems looks to be as complicated as the last. Currently, there is very little model consensus. It currently appears there will be two areas of low pressure, with a classic miller B track. Where the energy transfers will determine how much and what kind of precipitation will fall. As of now, it looks like the southern most portions of the region will get rain with some mixing of snow and sleet. Stay tuned.

Monday Night Technical Discussion

Synopsis

Warm air aloft will cause snow showers to change over to rain and freezing rain tonight except for northern counties where snow showers will persist. The precipitation will exit the state to the northeast Tuesday morning as scattered rain showers. Warm air advection will persist for Tuesday and temperatures will warm up. A cold front will move through Tuesday evening and bring cold air back into the area for the rest of the week. A northwesterly flow will persist for the end of the week, which will produce scattered lake effect snow showers Tuesday night through Friday morning. We will need to keep an eye on a system that will begin to approach the state from the southwest Sunday afternoon, which could bring us another batch of snow.

Short Term (Monday night through Tuesday night) 

As precipitation moves across the state to the northeast, warm air advection will cause precipitation to change over to rain and freezing rain for the majority of the state. Snow showers are likely to persist Monday night for northern counties and higher elevations. The 18Z NAM and the 18Z GFS are agreeing, as they have the precipitation east of the state by around 18Z. Any precipitation in the state after Tuesday morning will change over to scattered rain showers for the rest of the day. The state will warm up Tuesday afternoon and southeastern portions of the state will soar into the 50's for a high temperature. A cold front will pass through the area Tuesday evening and the cold air will return along with a northwesterly flow.

Long Term (Wednesday morning into the weekend)

The northwesterly flow will persist through Friday morning and provide a chance for scattered lake effect snow showers for northwestern counties. Lake effect snow showers could reach far southern counties Thursday night into Friday morning. Saturday looks to be calm and dry, but Sunday will be interesting due to a system approaching the state from the southwest. We will need to watch this system, as the 18Z GFS is indicating a large batch of snow falling across most of the state Sunday evening through Monday morning. 

~ Aaron Herbert

Monday PM Disco: Manic Monday of Snow and Sleet

Synopsis                                                                                     

With the winter storm pounding on us now, the questions  are "how much snow?' and "will there be much freezing rain or sleet?"  despite the snow falling across most of the central and eastern areas now, temperatures aloft will be on the rise, leaving room for more mixed precip later in the afternoon. the storm now is proving to be the biggest concern for us, as the rest of the week looks to be just cloudy and cool. A clipper system will threaten the south of the state by Thursday , so keep a watchful eye on this one, as it can bring a heavy burst of snowfall to our southern counties later this week.

Short Term (Now through Tuesday afternoon)

The storm is progressing through the state rather quickly, the 12z 4km NAM has the current radar signature happening at 2z, implying that it is about 7 hours too slow. If we compare that to how the 0z Euro and 12z GFS are doing now, they are also running slower than reality, showing that the storm could be out of the state before sunrise tomorrow. WAA aloft will be moderate throughout the evening, giving potential for more sleet and freezing rain as the evening hours come by, but the poor timing of this system in general implies that the advection is mishandled, but the updated 18z NAm shows colder 850 temps' than before, so sleet may only be in sporadic areas in the south central  counties. Surface WAA in the eastern counties will show that they will see mainly rain from this system, and in general, temperatures statewide will be omn the rise as the night rolls along, showing that freezing rain  will be more of an issue for us here in centre county, and in areas elsewhere in the centre region.  The dryslot with the system is pushing throught the western areas on a good quip, but the scattered light rain showers in ohio are puhing east with the system, which could show up in western PA, by tomorrow. Going into Tuesday, only a few snow showers will remain in northeastern PA,  

Longterm (Tuesday night into the Weekend)

The broad 500mg trough will help wrap around the blocking high that has been stretched along the north atlanitc last week, and this block will help keep that area in place for the entire week/. This will keep low clouds in the sky for most of the Northeast, and PA will be no exception. Dominant westerlies will take over with this trough, and any northerly component to those will help induce lake effect snow for Erie, moreso on Tuesday night going into Wednesday. Beyond this, a clipper looks to threaten the south by Wednesday overnight into Thursday, but the NA< resolves it as a weakening clipper from the 12z to 18z runs.   The clouds will keep state temps well below average for this time of year, and it will be one of the coldest ends to March in State College history.

Sun. Eve: Winter Ain't Over!

Synopsis

A mid-latitude cyclone gaining strength in the south-central Appalachians will mature as it heads north overnight. The winds will pick up and the wintry mix will begin from southwest to northeast: daybreak in Pittsburgh to four o'clock in the Poconos. The changeover from snow to a mix will be quicker west of the Allegheny Ridge and slower further east. This system will be gone in about 24 hours and we're left with drier and less windy conditions… except in the western half of the state, where back-end and lake-effect snows will occur on Wednesday. As for the long-range, models indicate the upper-level low will stall over the northeast US and result in lots of clouds and the occasional snow flurry.

Models Used: 12z ECMWF, 18z & 00z GFS, NAM, & Hi-Res NAM

Short Term

Model consensus with a warmer and slightly drier solution seems to be the most reasonable. Snow and ice accumulations will be light across the western third of the state where sleet and plain rain would dominate. The higher elevations in central PA will see heavy snow change over to moderate freezing grain, with snow accumulating 3-6 inches and ice accumulations of at least a tenth-inch. Eastern PA would see 2-5 inches of snow before the changeover to wintry mix with little additional ice and snow accumulations.

Long Range

Northwest flow over Lake Erie and the upper-level low stalling over PA will result in a dismal end-of-week for the Commonwealth.

-Jaron Breen

Thursday Afternoon Technical Discussion

Synopsis: For this upcoming weekend we can expect below normal temperatures with a couple storm systems coming through the region. Tonight we can expect partly clear conditions with diminishing winds overnight. Our next storm system, a clipper, will then enter the region late Friday night and continue into Saturday afternoon. Temperatures appear to be cold enough to support snow, so the threat exists for light accumulations with this system. Then, as we head into Monday a larger storm system will begin to affect the region. The precipitation will likely start as snow, then eventually change to rain. Keep in mind that this storm is still several days out, so a lot can change.

 Short Term: A weakening low centered over the Canadian Maritimes will be the source of strong, NW winds throughout the day. As this system moves further away, we can expect to see these winds diminish overnight. Low temperatures will dip into the low 20's as a result of weak cold air advection. Our next system is a clipper and will move through the region Friday night into late Saturday morning. The 18Z NAM run shows a colder trend as well as a southern dip affecting mainly the southern half of the Commonwealth. Light to moderate snow accumulations are possible with this system, especially in the higher terrain of the Laurel Highlands and Ridge and Valley Regions.

 

Long Term: After the clipper moves through, we will come under the influence of a weak area of high pressure. This high won't last long as a rapidly strengthening system over the Northern Plains moves to the ENE over the Great Lakes late Monday afternoon. A shortwave upper level disturbance is expected to trek ahead of this system moving in from the SW causing precipitation to begin earlier. Cold air is expected to still be in place to support some snow before changing to a mix of rain, then eventually all rain. This shortwave disturbance will then join the ENE moving storm system early Tuesday causing more precipitation that may be heavy at times. We will be affected by this storm's cold front around 12Z Tuesday. The 12Z EURO and GFS models show the potential for a changeover to snow at the wake of the cold front, but this should be nothing more than a nuisance.

Michael DiDomizio
The Pennsylvania State University | Class of 2013
B.S. Meteorology | Forecasting and Communications Option
Minor | Climatology

Thursday Morning Forecast

Synopsis: For this upcoming week we can expect at or below normal temperatures with a couple storm systems coming through the region. Today we can expect mostly cloudy, breezy conditions with a chance of flurries and cold temperature in the mid 30s. Our next storm system, a clipper will then enter the region late Friday and continue into Saturday afternoon. At the moment temperatures appear to be cold enough to support snow, so the threat exists for light accumulations with this system. Then as we head into Monday a larger storm system will begin to affect the region. The precipitation will likely start as snow and eventually change to rain. Keep in mind that this storm is still several days out, so a lot can change.

Short Term: A weakening low centered over the Canadian Maritimes will be the source of strong, NW winds throughout the day. Cold advection will remain in full force today with highs consequently struggling to reach 40 across much of the commonwealth. Expect scattered, lake-effect snow showers across the NW portions of PA throughout the day with little accumulation. Our next system will move through the region Friday night into Saturday morning in the form of a clipper. Current GFS runs show the system dipping farther south, bringing more precipitation, most likely in the form of snow, to southern PA.

Long Term: After the clipper moves through, we will come under the influence of a weak area of high pressure. This high won't last long, though, as a rapidly strengthening system over the Northern Plains moves to the NEover the Great Lakes. Past model runs (especially the ECMWF) swung this system up the coast, producing snowfall totals over a foot from the mid-Atlantic up into ME. But (unfortunately), the GFS and ECMWF have come into agreement regarding the track of the storm - moving NE over the lakes and swinging up into Canada. We will be affected by this storm's cold front around 12Z Tuesday. This is not the whole story, though... 00Z ECMWF and 06Z GFS both show a new center of low pressure developing just off the coast on Tuesday morning, bringing the potential for more than a foot of snow to portions of New England (and possibly NE PA).

Wed Night

Synopsis: Brief snow squalls are possible tomorrow as a shot of cold air moves into the region and lasts until late week. A brief warm up occurs by the weekend as a storm system approaches from the west.

Short Term: Cold air advection aloft, coupled with a upper level divergence from the left exit region of a jet streak, will cause snow squalls to move across the state tomorrow morning into afternoon. Higher elevation locations will see most of the accumulating snows, however a quick dusting is possible region-wide. Northwesterly flow will continue to usher in cold air and will provide breezy conditions through Thursday.

Long Term: Weak ridging on Friday will gradually warm the region up by the early weekend, when a shortwave dives down from the upper Midwest and scoots on through the region. Light precipitation can be expected with snow North of I-80, though there is some slight model discrepancy as to the exact track of this system. Another, stronger, system will approach the region early next week. model guidance is beginning to come into agreement with the solution, though there is still uncertainty as to precipitation types. As of now (using a blend of the GFS and EURO), it looks like a mostly rain event with a wintry mix in northern zones. 

Monday Night Technical Discussion

Synopsis

 

Rain showers will continue to push east across the state tonight. The associated cold front will move through the state behind the rain showers Tuesday morning and bring a change to scattered rain and snow showers across western Pennsylvania Tuesday night. The scattered snow showers will continue through Thursday morning as a northwesterly flow persists. A deep trough will dig south and bring cold air back to the region for the end of the week.  We will need to keep an eye out for Saturday afternoon, as another system threatens the state with a chance for a wintry mix of precipitation.

 

Short Term (Monday Night thru Wednesday Night)  

 

Scattered rain showers will continue to move across the state tonight as the associates cold front will push through Tuesday morning. Both the 18Z NAM and GFS agree with the rain showers exiting the state around 21Z on Tuesday. Some portions of the state could see over 1" of rain, with an average rainfall total of 0.5"-0.75" across the state. The cold front will bring scattered lake effect snow showers Tuesday night for the western portion of the state as a northwesterly flow sets up over the lakes. These scattered snow showers will persist through Thursday morning as a deep trough of cold air continues to dig south.

 

Long Term (Thursday into the Weekend)

 

Scattered lake effect snow showers will dissipate Thursday morning as the northwesterly flow weakens and high pressure moves in. Skies will begin to clear Thursday throughout the day setting up for partly clear skies Friday and warmer temperatures. A system could approach the area Saturday afternoon. We will need to watch closely, as the 18Z GFS is hinting at mixed precipitation across the state.

~Aaron Herbert

Sun. Eve: Big Changes Coming

Synopsis:

High pressure centered east of Boston and a warm front that has become stationary over western NY and NE PA have set-up a southwesterly flow, which will lead to one more day of above average highs before a powerful arctic front heads through overnight, the precipitation beginning around 00z. Temperatures will crash soon after the rain starts and the winds will also kick up. The precipitation will taper as a mix of rain and wet snow about 4-8 hours after arriving. Back-end snow showers will occur on Wednesday. Thursday will be quiet. And Friday could see a chance of a few snow showers from a passing upper-level disturbance.

Models Used: 00z & 18z NAM, 00z Hi-Res NAM, 15z & 21z SREF, 18z GFS, 12z ECMWF

Model Guidance:

The models were trustworthy. However, the 0.01-0.10 precipitation contour on the GFS was well ahead of the cold front – not the case on the NAM due to its finer grid scales. Therefore, the NAM & SREF were used in timing the onset and end to the cold front's precipitation. The NAM, unlike the GFS, showed holes in the back-end snows, again due to its finer grid spacing, making the GFS easier to interpret. The GFS & Euro both showed the end-of-week system, with the precipitation contours different due to the different resolutions of the models.

Short-Range:

The Hi-Res NAM reflectivity showed a chance of thundershowers in western PA, enhanced by orographic lift and weakened by the mountains. The potency (temperature gradient) of the cold front and the timing of the precipitation of 00z support thundershowers; the time of year, to a certain extent, does not. The rain will last for about six hours and the winds will be a factor over the course of the week.

Long-Range:

There's really nothing to add about the end-of-week disturbance except to watch the trends closely. The Euro was hinting at another pretty big batch of snow for early next week, also something to watch over the course of the week.

-Jaron Breen